Aperture Area cm² Optics Calculator
Measured unobscured annular pupil area in cm², not nominal filled disk or eye-normalized throughput. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Description
A central obstruction subtracts area from a telescope's circular collecting pupil.
A central obstruction subtracts area from a telescope's circular collecting pupil.1
Clear area does not include optical throughput, diffraction structure or obscuration by supports. Use Aperture Area cm² Optics Calculator to evaluate the supplied inputs under the model explained below.
When to use Aperture Area cm² Optics Calculator
Use Aperture Area cm² Optics Calculator to evaluate the supplied inputs under the model explained below. Establish the units, measurement scope and model assumptions before entering values.
How to use Aperture Area cm² Optics Calculator and understand its results
- Establish the units, measurement scope and model assumptions before entering values.
- Enter Aperture mm, Obstruction mm using the field table and validation rules below, then run the tool.
- Read Clear aperture area c m2; interpret the units, signs, ordering and unknown-value placeholders described below.
- Correct reported input errors and rerun. Apply successful results according to their specific meanings and check the assumptions before using them in a decision.
| Input field | Meaning | Value type | Requirement |
|---|---|---|---|
| apertureMm | Aperture mm | number | Required; constraints below |
| obstructionMm | Obstruction mm | number | Required; constraints below |
Enter positive aperture and nonnegative obstruction diameters in mm with obstruction<aperture. Compute π(aperture²−obstruction²)/400 for cm². No spiders, throughput, off-axis vignetting or usable resolution is assessed.
clearApertureCM2=π×(apertureMm²−obstructionMm²)/400 Use the field order, units and branch conditions described above.
| Output field | Meaning | Value type |
|---|---|---|
| clearApertureAreaCM2 | Clear aperture area c m2 | number |
{
"input": {
"apertureMm": 100,
"obstructionMm": 20
},
"output": {
"clearApertureAreaCM2": 75.39822368615503
}
}Limitations and assumptions
Clear area does not include optical throughput, diffraction structure or obscuration by supports. Apply the exact scope and assumptions explained above.
All listed fields require explicit values. Unexpected fields, incorrect types, nonfinite numbers and sparse arrays fail validation. Domain-specific bounds, alignments and supported tokens are explained above; extremely large inputs or outputs can also be rejected. Input errors differ from successful false results, empty match lists and unknown-evidence placeholders.
Alternative or Complementary methods
Use Light Gathering Power vs Eye Calculator for a related task: Clear collecting area and optical throughput affect relative photon collection.
Use Speckle Interferometry Diffraction Limit lambda/D Resolution Check for a related task: The Rayleigh relation describes ideal circular-aperture angular resolution.
References
-
Aperture Area cm² Optics Calculator — tool.io
Similar or alternative tools
- Light Gathering Power vs Eye Calculator
Clear collecting area and optical throughput affect relative photon collection.
- Speckle Interferometry Diffraction Limit lambda/D Resolution Check
The Rayleigh relation describes ideal circular-aperture angular resolution.